1. Field of the Invention
The present invention relates to a high-pressure crystallographic observation apparatus for observing the crystals of substances under a high pressure and, more specifically, to a high-pressure crystallographic observation apparatus such as for observing the forms of crystals and physical variations including processes of growth and extinction of crystals and for measuring the pressure of fusion of a solid by varying pressure at a constant temperature.
2. Description of the Related Art
Elucidation of forms of crystals and physical variations including processes of growth and extinction of crystals under pressure is very important for the manufacture or use of chemical substances under pressure.
For example, knowledge of such physical variations of crystals is an indispensable requirement of the pressure crystallization process, which has been a remarkable technique of separating a specified substance from a mixture and purifying the specified substance, because the pressure crystallization process is a separating and purifying process of producing a specified substance of high purity by separating the specified substance by crystallization from a liquid or slurry mixture by the agency of a high pressure. Accordingly, it is necessary to know in advance a pressure necessary for the separation and growth of crystals and a pressure condition for satisfactory crystallization.
Crystals are observed under pressure to obtain data representing the physical variations of the crystals under pressure.
Shown in FIG. 6 is a typical, conventional crystallographic observation apparatus for the observation of crystals under pressure. This crystallographic observation apparatus comprises a pressure vessel 130 provided with opposite, transparent observation window blocks 110 and 120 formed of a transparent material, and a pressurizing device 140 for enhancing the internal pressure of the pressure vessel 130. A pipe 150 is connected to the pressurizing device 140 to inject a sample to be observed into the pressurizing device 140. The pressurizing device 4 is connected to the pressure vessel 130 by a pressure pipe 160. The internal pressure of the pressure vessel 130 is measured by a pressure gauge 190 of an optional type connected to the pressure pipe 160.
This crystallographic observation apparatus is operated for the observation of crystals in the following manner. A sample is injected through the pipe 150 into the pressurizing device 140. The pressurizing device 140 supplies the sample through the pressure pipe 160 into the sample chamber 170 of the pressure vessel, and then the sample filled in the sample changer 170 is illuminated through the transparent observation window block 120 by a light source 180 to enable to observation of the sample with a microscope through the transparent observation window block 110.
Then, the pressurizing device 140 increases the internal pressure of the pressure vessel 130 to pressurize the sample filling the sample chamber 170. Crystallization progresses as the internal pressure is increased. The form of the crystals and the process of growth of the crystals are observed while the internal pressure of the sample chamber 170 is being increased. The process of extinction of the crystals is observed as the internal pressure of the sample chamber is decreased.
This conventional crystallographic observation apparatus, however, has the following disadvantages.
A comparatively large amount of sample is necessary to fill up the sample chamber of the pressure vessel by injecting the sample into the pressurizing device and supplying the sample through the pressure pipe to the sample chamber, because the pressurizing device and the pressure pipe must be filled up with the sample as well as the sample chamber.
In most cases, the sample for observation, as a matter of course, is a new substance, and it is difficult to prepare a large amount of such a new substance. In some cases, only a small amount of sample is available even if the sample is not a new substance. Accordingly, requiring a large amount of sample is a significant disadvantage.
A pipe having a very small inside diameter is used as the pressure pipe particularly when the crystallographic observation apparatus is used for observation under a high pressure. Therefore, a solid sample cannot be introduced in to the sample chamber. It is particularly difficult to introduce a slurry sample containing nonsoluble solid particles into the sample chamber due to high viscosity of the slurry sample.
Particularly, a liquid sample of a substance having a comparatively high melting point is liable to be caused to solidfiy within the pressure pipe even by slight decrease in temperature or by increase in pressure while the liquid sample is being injected through the pressure pipe, and often clogs the pressure pipe. Consequently, the pressurizing device is unable to increase the internal pressure of the sample chamber to a predetermined pressure. The solidification of the liquid sample may be obviated by heating the pressure pipe, which, however, may possibly entail excessive heating of the liquid sample. Accordingly, the pressure pipe must be heated for such a purpose under strict temperature control, which is very difficult. Heating the pressure pipe also heats the pressure gauge to make accurate pressure measurement impossible.
The interior of the pressurizing device, the pressure vessel and the pressure pipe must be washed perfectly after the completion of observation of a sample prior to the supply of another sample into the sample chamber of the pressure vessel, which requires much time because many parts must be washed. Washing the interior of the pressure pipe, in particular, is very difficult and requires much time because the pressure pipe has a very small inside diameter. Finish washing using the next sample requires an additional amount of sample for washing.
Furthermore, as shown in FIG. 6, the transparent observation window blocks of the conventional crystallographic observation apparatus is cylindrical and each transparent observation window block is seated on a flat seat, and hence the thickness of the transparent observation window blocks must be comparative large to secure a sufficient strength against pressure. Accordingly, the objective lens of the microscope is disposed inevitably at a comparatively long distance from the sample, so that the microscope is unable to be focused at a high magnification and hence the sample cannot sufficiently be magnified for observation.
The pressure of fusion of crystals is another very important data for the use and manufacture of a solid obtained by crystallization.
Shown in FIG. 7 is an essential portion of another conventional crystallographic observation apparatus capable of measuring the pressure of fusion. This crystallographic observation apparatus comprises, as principal components, a pressure vessel 172 having a sample chamber 182, a plunger 162 fitting the sample chamber 182, pressure measuring means, not shown, for measuring the internal pressure of the sample chamber 182, and pressing means, not shown, for pressing the plunger 162.
In measuring the pressure of fusion by the crystallographic observation apparatus, a liquid sample is poured into the sample chamber 182, the liquid sample is compressed by the plunger 162 for solidification, and then the internal pressure of the sample chamber 182 is reduced and, at the same time, the volume variation .DELTA.V of the sample chamber 182 and the internal pressure P of the sample chamber 182 are measured to determine the relation between .DELTA.V and P. The value of P corresponding to a point on a .DELTA.V-P curve where the volume of the sample chamber varies sharply with respect to the variation of pressure, namely, a discontinuous point on the .DELTA.V-P curve, corresponds to the pressure of fusion.
This conventional crystallographic observation apparatus, however, has the following disadvantages.
Indirectly measuring the pressure of fusion from the .DELTA.V-P relation, the crystallographic observation apparatus is unable to determine the pressure of fusion accurately, and hence this crystallographic observation apparatus has a basic problem that the accuracy of measurement is not high enough. Theoretically, a discontinuous point appears on the .DELTA.V-P curve at the pressure of fusion, howeve, practically, the gradient of the .DELTA.V-P curve in the vicinity of the pressure of fusion changes gradually instead of a sharp change and, at the worst, it occurs with some substances that the determination of the pressure of fusion is entirely impossible.